The present invention relates to a device for treating contaminated water by means of electroflotation wherein cathode electrodes are arranged above anode electrodes. The present invention also relates to a process for operating a device of this type.
Devices for treating contaminated water by means of electroflotation are known, for example, from Norwegian Patent Specification No. 92,995. In these known devices, the anode electrodes and cathode electrodes are located on the bottom of a flotation cell. The gas bubbles formed during electrolysis of the water, particularly hydrogen bubbles, attach themselves to the suspended matter present in the water, giving the suspended matter a relative density lower than that of water and carrying it to the surface. The floating materials are then skimmed from the surface of the water.
In these known devices, the electrodes, and in particular the cathode electrodes, must be cleaned approximately every 2 weeks. This is due to the fact that the effluent is almost always calcareous and extensive lime deposits form on the cathode electrodes. As the deposits form, the energy consumption of the device increases steadily since the voltage must be raised continuously in order to ensure constant current through the electrodes. To clean these known flotation cells, the cells must be emptied and the electrodes must be taken out.